Solid-state image sensor, manufacturing method for solid-state image sensor, and camera having plural color filters and dual transparent film

ABSTRACT

A solid-state image sensor includes a plurality of light-receiving elements arranged in a light-receiving area, and a plurality of micro-lenses corresponding to the light-receiving elements, and has a flattening film formed on the plurality of the micro-lenses. At a center of the light-receiving area, the micro-lenses are placed in positions directly above corresponding photodiodes, and placed in positions which are progressively offset from positions directly above the corresponding photodiodes, towards a center of the light receiving area, as micro-lenses are located farther from the center of the light-receiving area.

This application is a divisional of U.S. application Ser. No.10/909,311, filed Aug. 3, 2004 now U.S. Pat. No. 7,253,399.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a solid-state image sensor includingmicro-lenses for a plurality of light-receiving elements formed on asemiconductor substrate, and a manufacturing method thereof.

(2) Description of the Related Art

In recent years, miniaturization of cameras is progressing along withincrease in pixel count of solid-state image sensors.

With digital still cameras and camera-equipped mobile phones, ashortening of an exit pupil distance is progressing following theminiaturization of cameras. At this point, exit pupil refers to avirtual image of a lens (or stop) as seen from a light-receiving area,and exit pupil distance refers to a distance between the light-receivingarea and a lens (refer to FIG. 18).

FIG. 18 illustrates a cross-section diagram of a camera portion of amobile phone. A lens 110 is installed on a frame 111 of the mobilephone, and a CCD image sensor 112 is provided in an interior of themobile phone. A distance between the lens 110 and the CCD image sensor112 is an exit pupil distance D. Although incidence of light around acenter of the light-receiving area is perpendicular, a periphery of thelight-receiving area is limited to incidence of, not perpendicular, butoblique light.

FIG. 1 is a cross-section diagram illustrating a physical relationshipof light-receiving elements and micro-lenses in an existing solid-stateimage sensor for facilitating shortening of an exit pupil distance.Light rays from a light source in the diagram represent incident lightfrom a lens. The left side of the diagram represents a cross-section ofa central portion of valid pixels making up a light-receiving area, andthe right side represents a cross section of a peripheral portion ofvalid pixels making up the light-receiving area. As shown on the leftside of the diagram, an in-layer lens 3, a color filter 5, and amicro-lens 7 are formed directly above a light-receiving element 1, in acentral portion of the light-receiving area. Whereas in a peripheralportion of the light-receiving area, the in-layer lens 3, the colorfilter 5, and the micro-lens 7, are formed above the light-receivingelement 1, offset towards a center of the light-receiving area, as shownin the right side of the diagram. In this manner, an existingsolid-state image sensor forms a micro-lens in an offset position abovea light-receiving element in a CCD image sensor light-receiving area, asa countermeasure for shortening of exit pupil distance. With this, animprovement of a light-collection rate for incident oblique light in theperipheral portion of the light-receiving area is promoted.

Furthermore, in a solid-state image sensor disclosed in officialpublication of Japanese Laid-Open Patent Application No. 06-326284, atransparent film with a lower refractive index than micro-lens materialis provided, and deterioration of sensitivity upon lens stop release isminimized.

However, according to existing technology mentioned above, theshortening of exit pupil distance in response to slimming of mobilephone cameras and digital still cameras is reaching its threshold. Forexample, if the shortening of exit pupil distance should progressfurther with regard to the configuration in FIG. 1, the light-receivingelements will no longer be able to perform light-collection as intended,as shown in FIG. 2, and a problem of shading arises due to lack ofsensitivity in the peripheral portion of the light-receiving area. Inother words, from a center of an image, sensitivity deteriorates as aperiphery of the image is neared, and a deterioration of image qualityarises in which darkening worsens towards the periphery of the image.

In addition, due to the shortening of exit pupil distance, it isnecessary to perform mask alignment with greater precision during amicro-lens formation process to form micro-lenses that are offset inappropriate positions for a case in FIG. 2 as well, and positionalignment is becoming difficult in terms of design and production.

Furthermore, although deterioration of sensitivity upon lens stoprelease is reduced in the solid-state image sensor disclosed in officialpublication of Japanese Laid-Open Patent Application No. 06-326284, thesame problem exists with regard to the shortening of exit pupildistance.

SUMMARY OF THE INVENTION

In view of the aforementioned issues, an object of the present inventionis to provide a solid-state image sensor, a manufacturing methodthereof, and a camera, that makes possible shortening of exit pupildistance, with low shading.

In order to resolve the aforementioned issues, the solid-state imagesensor in the present invention is a solid-state image sensor includinga plurality of light-receiving elements arranged in a light-receivingarea, a plurality of micro-lenses corresponding to the light-receivingelements, and a flattening film formed on the plurality of micro-lenses,wherein the micro-lenses are placed in positions directly abovecorresponding light-receiving elements at a center of thelight-receiving area, and placed in positions which are progressivelyoffset from positions directly above corresponding light-receivingelements towards the center, as micro-lenses are located farther fromthe center.

Here, it is possible to have a structure wherein a refractive index ofthe flattening film is less than a refractive index of the micro-lenses.

According to this structure, shortening of exit pupil distance whilehaving low shading can be made possible through a combination ofincidence angle moderation by the flat film and an improvement of alight-collection rate through offsetting.

Here, it is possible to have a structure wherein the micro-lenses arearranged in a matrix, adjoining each other without gaps, in row andcolumn directions.

According to this structure, it is possible to further improve alight-collection rate of the micro-lens.

Here, it is possible to have a structure where the solid-state imagesensor further includes in-layer lenses formed between the micro-lensesand the light-receiving elements, wherein the in-layer lenses are placedin positions directly above the corresponding light-receiving elementsat the center of the light-receiving area, and placed in positions whichare progressively offset from the positions directly above thecorresponding light-receiving elements towards the center, as in-layerlenses are located farther from the center, and the offset of eachmicro-lens is greater than the offset of corresponding in-layer lens.

According to this structure, shortening of exit pupil distance whilehaving low shading can be made possible even in a structure having twoor more layers of micro-lenses or two or more layers of in-layer lenses.

Here, it is possible to have a structure wherein at least one of acurvature and a thickness of the micro-lenses is greater than acurvature and thickness of the in-layer lenses.

According to this structure, it is possible to further improve thelight-collection rate of the micro-lens.

Here, it is possible to have a structure wherein the micro-lenses alsoserve as color filters.

According to this structure, elimination of the color filter layerallows for just as much thinning of the solid-state image sensor.

Furthermore, the manufacturing method for the solid-state image sensorin the present invention has the same structuring effect as thatmentioned above, for a camera provided with a solid-state image sensor.

According to the solid-state image sensor in the present invention,shortening of exit pupil distance while having low shading can be madepossible through the combination of the incidence angle moderation bythe flat film and the improvement of light-collection rate in theperipheral portion of the light-receiving area through micro-lensoffsetting.

FURTHER INFORMATION ABOUT TECHNICAL BACKGROUND TO THIS APPLICATION

The disclosure of Japanese Patent Application No. 2003-285555 filed onAug. 4, 2003, including specification, drawings and claims, isincorporated herein by reference in its entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, advantages and features of the invention willbecome apparent from the following description thereof taken inconjunction with the accompanying drawings that illustrate specificembodiments of the invention.

In the Drawings:

FIG. 1 is a cross-section diagram of an existing solid-state imagesensor.

FIG. 2 is a cross-section diagram of an existing solid-state imagesensor.

FIG. 3 is a cross-section diagram of a solid-state image sensor in afirst embodiment of the present invention.

FIG. 4 is a diagram illustrating a manufacturing process for thesolid-state image sensor of the first embodiment.

FIG. 5 is a diagram illustrating a continuation of the manufacturingprocess for the solid-state image sensor of the first embodiment.

FIG. 6 is a diagram illustrating a variation of the manufacturingprocess for the solid-state image sensor of the first embodiment.

FIG. 7 is a cross-section diagram of a solid-state image sensor in asecond embodiment of the present invention.

FIG. 8 is a diagram illustrating a manufacturing process for thesolid-state image sensor of the second embodiment.

FIG. 9 is a diagram illustrating a continuation of the manufacturingprocess for the solid-state image sensor of the second embodiment.

FIG. 10 is a diagram illustrating a variation of the manufacturingprocess for the solid-state image sensor of the second embodiment.

FIG. 11 is a cross-section diagram of a solid-state image sensor in athird embodiment of the present invention.

FIG. 12 is a diagram illustrating a manufacturing process for thesolid-state image sensor of the third embodiment.

FIG. 13 is a diagram illustrating a continuation of the manufacturingprocess for the solid-state image sensor of the third embodiment.

FIG. 14 is a diagram illustrating a variation of the manufacturingprocess for the solid-state image sensor of the third embodiment.

FIG. 15 is a cross-section diagram of a solid-state image sensor in afourth embodiment of the present invention.

FIG. 16 is a diagram illustrating a manufacturing process for thesolid-state image sensor of the fourth embodiment.

FIG. 17 is a diagram illustrating a variation of the manufacturingprocess for the solid-state image sensor of the fourth embodiment.

FIG. 18 is a diagram illustrating a physical relationship of a cameralens and a CCD image sensor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

(Structure of a Solid-State Image Sensor)

FIG. 3 is a diagram representing a cross-section of a solid-state imagesensor in a first embodiment of the present invention. This solid-stateimage sensor includes a light-receiving area in which light-receivingelements (photodiodes) are arranged two-dimensionally. The diagramrepresents a cross-section of two light-receiving elements in a centralportion (diagram, left) and a cross-section of two light-receivingelements in a peripheral portion (diagram, right) of the light-receivingarea. Furthermore, solid lines in the diagram schematically representincident light from a light source (equivalent to the lens 110 shown inFIG. 18).

The solid-state image sensor in the same diagram is formed by stacking,a flattened transparent insulating film (protective film) 2 which ismade out of material such as boron phosphate silicate glass (BPSG), anin-layer lens 3 having a high refractive index (n=1.5 to 2.0) and convexshape, an in-layer lens flat film 4 made out of an acrylic transparentresin, a color filter 5 made out of a color resist containing a dye orpigment, a transparent film 6 made out of an acrylic transparent resin,a micro-lens (also known as a top lens) 7, and a flattening film 8, inthe order of mention, above a photodiode 1 formed on a siliconsemiconductor substrate 10. This enables shortening of an exit pupildistance (1) by having the flattening film 8 above the micro-lens 7, and(2) arranging the in-layer lens 3, color filter 5, and micro-lens 7, inpositions that are offset towards a center, with this offset increasingwith proximity to a periphery of the light-receiving area. Moreover, asize of individual cells including a single photodiode is, for example,about 3 μm in length and width, or less, and a distance from thephotodiode 1 to a bottom of the micro-lens 7 is in the area of about 3to 5 μm.

To explain more specifically regarding (1), the flattening film 8 makesuse of a material having a lower refractive index than material of themicro-lens 7 (n=1.6 to 1.7). For example, the material of the flatteningfilm 8 is an acrylic resin with a refractive index of n=1.4 to 1.5. Assuch, although only incident light with a large incidence angle(assuming 0 degrees at a perpendicular direction to the light-receivingarea) incidents in a periphery of valid pixels within thelight-receiving area, the incidence angle towards the micro-lens 7 canbe moderated (reduced) by passing the incident light having a largeincidence angle, through the flattening film 8, as shown on the rightside of the diagram. Furthermore, the in-layer lens flat film 4 makesuse of a material having a lower refractive index than material of thein-layer lens 3. For example, the material of the in-layer lens flatfilm 4 is an acrylic resin with a refractive index of n=1.4 to 1.5.

To explain more specifically regarding (2), in a center of the validpixels within the light-receiving area, the in-layer lens 3, the colorfilter 5, and the micro-lens 7, are formed in positions stacked directlyabove the photodiode 1, as shown on the left side of the diagram. Incontrast, in the periphery of the valid pixels within thelight-receiving area, the in-layer lens 3, the color filter 5, and themicro-lens 7 are formed offset towards the center, as shown on the rightside of the diagram. This amount of offset, with regard to theindividual in-layer lens 3, color filter 5, and micro-lens 7, is largestat the periphery, becomes smaller as the center is neared, and is “0” atthe center. Furthermore, the offset increases with a higher layer, fromthe in-layer lens 3, the color filter 5, and micro-lens 7, in thatorder. With this offsetting, light-collection in the photodiode 1 can beperformed efficiently for incident light with a large incidence angle inthe periphery.

In addition, as another mechanism for improving a rate oflight-collection in the solid-state image sensor in the diagram, asidefrom (1) and (2), (3) two-dimensionally arranged micro-lenses 7 areformed adjacent each other in columns and rows in such a way that nogaps are left therebetween. In addition, (4) each micro-lens 7 is formedwith a greater curvature and thickness than the in-layer lens 3. In thismanner, an improvement of the light-collection rate is promoted throughan increase, as much as possible, of the diameter, and an increase ofthe curvature and thickness of the micro-lens 7, combined with theaforementioned (1) and (2).

As explained so far, according to the solid-state image sensor in thepresent embodiment, it is possible to improve sensitivity in theperipheral portion of the light-receiving area even for oblique lighthaving larger incidence angles, by combining incidence angle moderationthrough the flattening film 8 and the above-mentioned light-collectionrate improvement. As a result, shortening of an exit pupil distance ismade possible while suppressing shading.

(Manufacturing Method of the Solid-State Image Sensor)

FIG. 4, (a) to (c), and FIG. 5, (d) to (e), are diagrams illustratingcross-sections of the solid-state image sensor in the first embodiment,in a manufacturing sequence. These manufacturing processes are explainedin (11) to (15) below.

(11) As shown in FIG. 4 (a), an in-layer lens 3 is formed, and anin-layer lens flat film 4 is formed on the in-layer lens 3. At thispoint, the in-layer lens 3 is formed by using a mask (first mask) inwhich forming positions of the in-layer lens 3 are offset towards acenter, with this offset increasing with proximity to a periphery of alight-receiving area. The in-layer lens flat film 4 is formed byapplication of an acrylic resin, for example.

(12) As shown in FIG. 4 (b), a color filter 5 is formed on top of thein-layer lens flat film 4. For example, in a case of the Bayer Array,which is typical of a primary color filter using the three colors, red,green, and blue (RGB), color resist application, exposure, anddevelopment is repeated for each of the colors R, G, and B. During thisexposure, a mask (second mask) is used in which forming positions of thecolor filter 5 are offset towards the center, with this offsetincreasing with proximity to the periphery of the light-receiving area.Here, the offset of the second mask is larger than that of the firstmask.

Accordingly, color filters corresponding to each photodiode 1 areformed.

Moreover, it is the same in a case where a complementary color filter,not a primary color filter, is formed. For example, in a complementarycolor checkered array that is typical as a complementary color filter,color resist application, exposure, and development can just be repeatedfor four colors, namely, green (G), and each of complementary colorsyellow (Ye), magenta (Mg), and cyan (Cy).

(13) As shown in FIG. 4 (c), a transparent film 6 is formed on the colorfilter 5. This is done through application of an acrylic resin, forexample.

(14) As shown in FIG. 5 (d), a micro-lens 7 is formed on the transparentfilm 6. To be specific, after forming a lens layer only on micro-lensplacement positions by applying, exposing and developing, 1 to 2 μm of aphenolic resin (refractive index n=1.5 to 1.7) as a resist, a curvedsurface of the lens is formed by thermal flow processing. During thisexposure, a mask (third mask) is used in which forming positions of themicro-lens 7 are offset towards the center, with this offset increasingwith proximity to the periphery of the light-receiving area. Here, thethird mask has a larger offset than the second mask.

(15) As shown in FIG. 5 (e), a flattening film 8 is formed on themicro-lens 7. To be specific, the flattening film 8 is formed byapplying a 1 to 2 μm transparent film of acrylic resin (refractive indexn=1.4 to 1.5).

The solid-state image sensor shown in FIG. 3 can be manufactured throughthe aforementioned manufacturing process.

(Variation of the Manufacturing Method)

Moreover, processes in (15a) and (16) can be performed in place ofaforementioned process (15), in the manufacturing method shown in FIG. 4and FIG. 5. FIG. 6, (e) to (f), is a diagram illustrating cross-sectionsfor the processes in (15a) and (16), in this variation. Hereinafter,(15a) and (16) shall be explained.

(15a) As shown in FIG. 6 (e), a flattening film 8 is formed on amicro-lens 7. To be specific, a 0.5 to 2 μm transparent film of acrylicresin (refractive index n=1.4 to 1.5) is applied.

(16) As shown in FIG. 6 (f), film thickness is adjusted by etching thisapplied transparent film. Moreover, (15a) and (16) can be repeated. Withthis, the film thickness of the flattening film 8 can be preciselyadjusted.

In this manner, the solid-state image sensor shown in FIG. 3 can bemanufactured, and the film thickness of the flattening film 8 can beaccurately optimized, even through the present variation.

Second Embodiment

(Structure of a Solid-State Image Sensor)

FIG. 7 is a cross-section diagram of a solid-state image sensor in asecond embodiment of the present invention. This structure in the samediagram is different in comparison to the structure in FIG. 3, in havingthe color filter 5 omitted, and having a micro-lens 7 a in place of themicro-lens 7. Hereinafter, explanation shall be made centering on thesepoints of difference, with explanation on points of similarity beingomitted.

The micro-lens 7 a is different from the micro-lens 7 in that, beingnon-transparent, it also serves as a color filter.

According to this structure, as the micro-lens 7 a also serves as acolor filter, reduction of one color filter layer's worth of thicknessfurthers thinning of the solid-state image sensor, in addition toenabling shortening of an exit pupil distance while also being able tolimit shading as in the first embodiment. For example, in a case where adistance from the photodiode 1 to the bottom of the micro-lens 7 of thesolid-state image sensor in the first embodiment is 3.0 to 5.5 μm, thesolid-state image sensor in the second embodiment can be a slimmed downto a 2.0 to 4.5 μm thin-film. As a result, color mixing of light passingthrough color filters of adjacent photodiodes can be reduced, and imagequality can be improved.

(Manufacturing Method of the Solid-State Image Sensor)

FIG. 8, (a) to (c), and FIG. 9, (d) to (f), are diagrams illustrating amanufacturing process of the solid-state image sensor of the secondembodiment. Such manufacturing process shall be explained in (21) to(26) below.

(21) As shown in FIG. 8 (a), an in-layer lens 3 is formed, on which anin-layer lens flat film 4 is formed. As this process is the same as thatin (11) mentioned previously, detailed explanation shall be omitted.

(22) As shown in FIG. 8 (b), a color resist 7R is applied (0.5 to 2.0μm) on the in-layer lens flat film 4. FIG. 8 (b) shows a case where R(red) color resist is applied.

(23) The color resist 7R is only formed above photodiodes correspondingto R (red) by exposing and developing this applied color resist 7R.During this exposure, a mask (second mask) is used in which formingpositions of the color resist are offset towards a center, with thisoffset increasing with proximity to a periphery of the light-receivingarea.

(24) As shown in FIG. 8 (c), even with regard to G (green) and B (blue),a color resist is formed above photodiodes corresponding to each colorby performing application, exposure, and development of the color resistin the same manner. Although only two pixels for R and G are representedin FIG. 8 (c), the color resist for each of the colors RGB is formed.

(25) As shown in FIG. 9 (d), a shape of a micro-lens is formed on top ofa color resist through application, exposure, development, and thermalflow processing of a resist that can be subjected to thermal flowprocessing (e.g., a phenolic resin).

(26) As shown in FIG. 9 (e), this lens shape can be transferred to thecolor resist by etching back. With this, a micro-lens 7 a is formed.

(27) As shown in FIG. 9 (f), a flattening film 8 is formed on amicro-lens 7 a. As this process is the same as that in (15) mentionedpreviously, detailed explanation shall be omitted.

The solid-state image sensor shown in FIG. 7 can be manufactured throughthe aforementioned manufacturing process. Moreover, although a case ofprimary color filters is explained in the aforementioned process (23)and (24), a complementary color filter can also be formed in the samemanner as previously explained in (12).

(Variation)

Moreover, processes in (27a) and (28) can also be performed in place ofthe aforementioned process (27) in the manufacturing method shown inFIG. 8, (a) to (c), and FIG. 9, (d) to (f). FIG. 10, (f) to (g), is adiagram illustrating cross-sections of processes in (27a) and (28) inthis variation. Hereinafter, explanation shall be made regarding (27a)and (28).

(27a) As shown in FIG. 10 (f), a flattening film 8 is formed on amicro-lens 7 a. To be specific, a 0.5 to 2 μm transparent film ofacrylic resin (refractive index n=1.4 to 1.5) is applied.

(28) As shown in FIG. 10 (g), film thickness is adjusted by etching thisapplied transparent film. Moreover, (27a) and (28) can be repeated. Withthis, the film thickness of the flattening film 8 can be preciselyadjusted.

In this manner, the solid-state image sensor shown in FIG. 7 can bemanufactured, and the film thickness of the flattening film 8 can beaccurately optimized, even through the present variation.

Third Embodiment

(Structure of a Solid-State Image Sensor)

FIG. 11 is a cross-section diagram of a solid-state image sensor in athird embodiment of the present invention. This structure in the samediagram is different in comparison to the structure in FIG. 3 in havingthe color filter 5 omitted, and having an in-layer lens 3 a in place ofthe in-layer lens 3. Hereinafter, explanation shall be made centering onthese points of difference, with explanation on points of similaritybeing omitted.

The in-layer lens 3 a is different from the in-layer lens 3 in that,being non-transparent, it also serves as a color filter.

According to this structure, as the in-layer lens 3 a also serves as acolor filter, reduction of one color filter layer's worth of thicknessfurthers thinning of the solid-state image sensor, in addition toenabling the shortening of an exit pupil distance while also being ableto limit shading as in the first embodiment. For example, in a casewhere a distance from the photodiode 1 to the bottom of the micro-lens 7of the solid-state image sensor in the first embodiment is 3.0 to 5.5μm, the solid-state image sensor in the third embodiment can be slimmeddown to a 2.0 to 4.5 μm thin-film. As a result, color mixing of lightpassing through color filters of adjacent photodiodes can be reduced,and image quality can be improved. In addition, as a distance of thein-layer lens 3, which is a color filter, and the photodiode 1 is shortin the solid-state image sensor in the third embodiment compared to thesolid-state image sensor in the second embodiment, color mixing can befurther reduced.

(Manufacturing Method of the Solid-State Image Sensor)

FIG. 12, (a) to (d), and FIG. 13, (a) to (h), are diagrams illustratingcross-sections of the solid-state image sensor of the third embodiment,in manufacturing sequence. These manufacturing processes are explainedin (31) to (39) below.

(31) As shown in FIG. 12 (a), a color resist 3R is applied (0.5 to 2 μm)on insulating film 2. A case where R (red) color resist is applied isshown.

(32) The color resist 3R is only formed above photodiodes correspondingto R (red) by exposing and developing this applied color resist 3R.During this exposure, a mask (first mask) is used in which formingpositions of the color resist are offset towards a center, with thisoffset increasing with proximity to a periphery of a light-receivingarea.

(33) As shown in FIG. 12 (b), even with regard to G (green) and B(blue), a color resist is formed above photodiodes corresponding to eachcolor by performing application, exposure, and development of colorresist 3G and 3B in the same manner. Although only two pixels for R andG are represented in FIG. 12 (b), a color resist for each of the colorsRGB is formed.

(34) As shown in FIG. 12 (c), an in-layer lens shape is formed on top ofa color resist through application, exposure, development, and thermalflow processing of a resist that can be subjected to thermal flowprocessing (e.g., a phenolic resin). A mask having the same offset asthe aforementioned first mask is also used during this exposure.

(35) As shown in FIG. 12 (d), an in-layer lens shape can be transferredto the color resist by etching. With this, an in-layer lens 3 a isformed.

(36) As shown in FIG. 13 (e), an in-layer lens flat film 4 is formed onthe in-layer lens 3 a.

(37) As shown in FIG. 13 (f), micro-lens material is applied onto thein-layer lens flat film 4.

(38) As shown in FIG. 13 (g) a micro-lens 7 is formed by exposure,development, and thermal flow processing of this applied micro-lensmaterial. As the process in (38) is the same as that in (14) mentionedpreviously, detailed explanation shall be omitted.

(39) As shown in FIG. 13 (h), a flattening film 8 is applied onto themicro-lens. As this process is the same as that in (15), detailedexplanation shall be omitted.

The solid-state image sensor shown in FIG. 11 can be manufacturedthrough the manufacturing process mentioned above. Moreover, although acase of primary color filters is explained in the aforementionedprocesses in (31) to (33), a complementary color filter can also beformed in the same manner as previously explained in (12).

(Variation)

Moreover, processes in (39a) and (40) can also be performed in place ofthe process in (39) mentioned previously, in the manufacturing methodshown in FIG. 12, (a) to (d), and FIG. 13, (e) to (h). FIG. 14, (h) to(i), is a diagram illustrating cross-sections for the processes in (39a)and (40) in this variation. Hereinafter, explanation shall be maderegarding (39a) and (40).

(39a) As shown in FIG. 14 (h), a flattening film 8 is formed on amicro-lens 7. To be specific, a 0.5 to 2 μm transparent film of acrylicresin (refractive index n=1.4 to 1.5) is applied.

(40) As shown in FIG. 14 (i), film thickness is adjusted by etching thisapplied transparent film. Moreover, (39a) and (40) can be repeated. Withthis, the film thickness of the flattening film 8 can be preciselyadjusted.

In this manner, the solid-state image sensor shown in FIG. 11 can bemanufactured, and the film thickness of the flattening film 8 can beaccurately optimized, even through the present variation.

Fourth Embodiment

(Structure of a Solid-State Image Sensor)

FIG. 15 is a cross-section diagram of a solid-state image sensor in afourth embodiment of the present invention. In comparison to thestructure in FIG. 11, structure in the same diagram is different inhaving the in-layer lens flat film 4, the color filter 5, and themicro-lens 7 omitted, and having a flattening film 8 above an in-layerlens 3. Furthermore, as the flattening film 8 can be of the samematerial as the in-layer lens flat film 4, it can also be said thatcompared with the structure in FIG. 11, the solid-state image sensor ofthe fourth embodiment assumes a structure in which the micro-lens 7 andthe flattening film 8 are omitted.

According to this structure, in addition to enabling shortening of anexit pupil distance while also being able to limit shading as in thefirst embodiment, further thinning of the solid-state image sensor canbe realized due to a difference in having a single layer of the in-layerlens 3 a instead of two layers of the micro-lens 7 and the in-layer lens3.

(Manufacturing Method of the Solid-state Image Sensor)

FIG. 16, (a) to (e), is a diagram illustrating cross-sections of thesolid-state image sensor of the fourth emodiment, in manufacturingsequence. These manufacturing processes are explained in (41) to (46)below.

(41) As shown in FIG. 16 (a), a color resist 3R is applied (0.5 to 2 μm)on insulating film 2. As this process is the same as that in (31),detailed explanation shall be omitted.

(42) The color resist 3R is only formed above photodiodes correspondingto R (red) by exposing and developing this applied color resist 3R. Asthis process is the same as that in (32), detailed explanation shall beomitted.

(43) As shown in FIG. 16 (b), even with regard to G (green) and B(blue), a color resist is formed above photodiodes corresponding to eachcolor by performing application, exposure, and development of the colorresist 3G and 3B in the same manner. As this process is the same as thatin (33), detailed explanation shall be omitted.

(44) As shown in FIG. 16 (c), an in-layer lens shape is formed on top ofa color resist. As this process is the same as that in (34), detailedexplanation shall be omitted.

(45) As shown in FIG. 16 (d), an in-layer lens 3 a is formed bytransferring a shape of the formed in-layer lens to the color resist. Asthis process is the same as that in (35), detailed explanation shall beomitted.

(46) As shown in FIG. 16 (e), a flattening film 8 is formed on thein-layer lens 3 a. As this process is the same as that in (15), detailedexplanation shall be omitted.

The solid-state image sensor shown in FIG. 11 can be manufacturedthrough the manufacturing process mentioned above. Moreover, although acase of primary color filters is explained in the aforementionedprocesses in (41) to (43), a complementary color filter can also beformed in the same manner as previously explained in (12).

(Variation)

Moreover, processes in (46a) and (47) can also be performed in place ofthe process in (46) mentioned previously in the manufacturing methodshown in FIG. 16 (a) to (e). FIG. 17 (e) to (f) is a diagramillustrating cross-sections for the processes in (46a) and (47) in thisvariation.

(46a) As shown in FIG. 17 (e), a flattening film 8 is formed on anin-layer lens 3 a. To be specific, a 0.5 to 2 μm transparent film ofacrylic resin (refractive index n=1.4 to 1.5) is applied.

(47) As shown in FIG. 17 (f), film thickness is adjusted by etching thisapplied transparent film. Moreover, (46a) and (47) can be repeated. Withthis, the film thickness of the flattening film 8 can be preciselyadjusted.

In this manner, the solid-state image sensor shown in FIG. 11 can bemanufactured, and the film thickness of the flattening film 8 can beaccurately optimized, even through the present variation.

Furthermore, although primary color filters and complementary colorfilters are explained as examples of color filters, primary colorfilters can be used for solid-state image sensors that prioritize colortone, and a complementary color scheme can be used in a solid-stateimage sensor that prioritizes resolution and sensitivity.

Furthermore, color resists that contain a dye, color resists thatcontain a pigment, and the like, exist as material for forming the colorfilter 5, and any of such options is possible. Furthermore, a colorfilter can also be formed by dyeing a dyeable transparent resist.

Although only some exemplary embodiments of this invention have beendescribed in detail above, those skilled in the art will readilyappreciate that many modifications are possible in the exemplaryembodiments without materially departing from novel teachings andadvantages of this invention. Accordingly, all such modifications areintended to be included within the scope of this invention.

INDUSTRIAL APPLICABILITY

The present invention is suitable for a solid-state image sensorpossessing a micro-lens on each of a plurality of light-receivingelements formed on a semiconductor substrate, a manufacturing methodthereof, and a camera with such a solid-state image sensor, and issuitable, for example, for a CCD image sensor, an MOS image sensor, adigital still camera, a built-in mobile phone camera, a built-innotebook computer camera, a camera unit connected to an informationprocessing device, and the like.

1. A solid-state image sensor comprising: light-receiving elementsarranged in a light-receiving area; in-layer lenses on said light-receiving elements; color filters above said in-layer lenses;micro-lenses on said color filters; a first transparent film on saidmicro-lenses; and a second transparent film between said in-layer lensesand said color filters, wherein, in a central portion of saidlight-receiving area a corresponding one of said micro-lenses isdirectly above a corresponding one of said light-receiving elements, andin a portion of said light-receiving area that is closer to a peripheryof said light-receiving area than a center of said light-receiving areacorresponding ones of said micro-lenses are offset from directly abovecorresponding ones of said light-receiving elements towards the centerof said light-receiving area, and wherein said color filters are formednot on an uneven surface resulting from said in-layer lenses, but onsaid second transparent film.
 2. The solid-state image sensor accordingto claim 1, wherein said second transparent film has a flat surface. 3.The solid-state image sensor according to claim 1, wherein in saidcentral portion of said light-receiving area a corresponding one of saidin-layer lenses is directly above said corresponding one of saidlight-receiving elements, and in said portion of said light-receivingarea that closer to the periphery of said light-receiving area than thecenter of said light-receiving area corresponding ones of said in-layerlenses are offset from directly above corresponding ones of saidlight-receiving elements towards the center of said light-receivingarea, with an amount of offset of each of said corresponding ones ofsaid in-layer lenses being less than an amount of offset of a respectiveone of said corresponding ones of said micro-lenses.
 4. The solid-stateimage sensor according to claim 1, wherein in said central portion ofsaid light-receiving area a corresponding one of said color filters isdirectly above said corresponding one of said light-receiving elements,and in said portion of said light-receiving area that is closer to theperiphery of said light-receiving area than the center of saidlight-receiving area corresponding ones of said color filters are offsetfrom directly above corresponding ones of said light-receiving elementstowards the center of said light-receiving area, with an amount ofoffset of each of said corresponding ones of said color filters beingless than an amount of offset of a respective one of said correspondingones of said micro-lenses.
 5. The solid-state image sensor according toclaim 1, wherein in said central portion of said light-receiving area acorresponding one of said in-layer lenses is directly above saidcorresponding one of said light-receiving elements, and in said portionof said light-receiving area that is closer to the periphery of saidlight-receiving area than the center of said light-receiving areacorresponding ones of said in-layer lenses are offset from directlyabove corresponding ones of said light-receiving elements towards thecenter of said light-receiving area, and in said central portion of saidlight-receiving area a corresponding one of said color filters isdirectly above said corresponding one of said light-receiving elements,and in said portion of said light-receiving area that is closer to theperiphery of said light-receiving area than the center of saidlight-receiving area corresponding ones of said color filters are offsetfrom directly above corresponding ones of said light-receiving elementstowards the center of said light-receiving area, with an amount ofoffset of each of said corresponding ones of said color filters beinggreater than an amount of offset of a respective one of saidcorresponding ones of said in-layer lenses.
 6. The solid-state imagesensor according to claim 1, wherein said first transparent filmcomprises a transparent flattening film.
 7. The solid-state image sensoraccording to claim 1, wherein a refractive index of said firsttransparent film is less than a refractive index of said micro-lenses.8. The solid-state image sensor according to claim 1, wherein a size ofan individual cell including one of said light-receiving elements is atmost 3 μm in both length and width.
 9. The solid-state image sensoraccording to claim 1, wherein a distance from one of saidlight-receiving elements to a bottom of a corresponding one of saidmicro-lenses is within a range of from 3 μm inclusive to 5 μm inclusive.10. The solid-state image sensor according to claim 1, wherein saidsolid-state image sensor is a CCD-type image sensor.
 11. The solid-stateimage sensor according to claim 1, wherein said solid-state image sensoris an MOS-type image sensor.
 12. The solid-state image sensor accordingto claim 1, wherein said light-receiving elements, in-layer lenses,mirco-lenses and first and second transparent films are constructed andarranged such that when oblique light enters the solid-state imagesensor from above the solid-state image sensor at the periphery of saidlight-receiving area, the oblique light is refracted towards saidlight-receiving elements by said first transparent film and furtherrefracted towards said light-receiving elements by said micro-lenses.13. The solid-state image sensor according to claim 12, wherein saidlight-receiving elements, in-layer lenses, micro-lenses and first andsecond transparent films are constructed and arranged such that theoblique light refracted by said micro-lenses is further refractedtowards said light-receiving elements by said in-layer lenses.